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A study suggests that monsoon-related riverine dynamics might have played a role in the collapse of the Indus civilization, one of the earliest urban civilizations that thrived during the Bronze Age. Urban settlements in the Indus or Harappan civilization flourished in the western parts of the Indo-Gangetic Plainan area spanning parts of India, Pakistan, Nepal and Bangladeshfor nearly 600 years. But beginning 3,900 years ago, the settlements were largely abandoned and a significant shift to the east began. Liviu Giosan and colleagues combined field surveys, satellite data, and dating techniques to investigate how climate-driven changes in the dynamics of water flow, erosion, and deposition in the region’s rivers led to the decline of the Harappans, an agrarian culture that reached its urban zenith – with architecturally sophisticated urban centers and a robust trade system – between 4,500 and 3,900 years ago. Contrary to suggestions that a large glacier-fed Himalayan river, thought by some to be the mythical Sarasvati, served the Harappan heartland, the authors found that only monsoon-fed rivers flowed through the region at the time. As the rivers dried with the waning monsoons, agriculture along their courses likely suffered, leading to shrinking settlements and a gradual eastward move to the monsoon-drenched regions below the Himalayas. The findings suggest that riverine dynamics likely contributed to the decline of the Indus civilization. See Giosan, L., Clift, P., Macklin, M., Fuller, D., et al., 2012, Fluvial Landscapes of the Harappan Civilization, Proceedings of the National Academy of Sciences, 10.1073/pnas.1112743109.

Highlights Proceedings of the National Academy of Sciences (PNAS): http://www.pnas.org/site/misc/current.shtml#Land